Tyan k8sr lockups

[Gary Mu1der]

All,

Well I can just now reliably hang (no panic, have to reset) my shiny new 
AMD64 dual processor box (2 x Opteron 246, Tyan Thunder K8S PRO, 6GB, 
Adaptec 2200S) with a simple dd of /dev/mem:

$ uname -a
FreeBSD d10.bidx.com 5.3-RELEASE FreeBSD 5.3-RELEASE #0: Fri Nov  5 
04:19:18 UTC 2004 
root at harlow.cse.buffalo.edu:/usr/obj/usr/src/sys/GENERIC  i386

$ dd if=/dev/mem of=/dev/null bs=1024k

(hang after about 5 seconds of watching it via top)

How do I force a kernel dump or get other diagnostics? The keyboard 
doesn't seem to respond.

Thought it might be due to the fact that I wasn't using a AMD64 kernel, 
but the same command crashes the following:

$ uname -a
FreeBSD d10.bidx.com 5.3-RELEASE FreeBSD 5.3-RELEASE #0: Fri Nov  5 
03:50:01 UTC 2004 
root at fanboy.samsco.home:/usr/obj/usr/src/sys/GENERIC  amd64

I ran memtest+ over night for 16 hours last night with no reported 
memory errors.

Gary